Fix a Blurry Logo in Your Outlook Signature

Updated June 2026

You built a signature, dropped in your logo, and it looks fine — until you view it on another machine, or your recipient replies and your logo has turned into a fuzzy smear. This is one of the most common signature problems on Windows, and it has a specific, fixable cause.

Why Outlook blurs signature images

Three things stack up against you, and they compound:

1. Windows display scaling. Most modern laptops ship with display scaling at 125% or 150% (Settings → System → Display). Classic Outlook renders email with Microsoft Word’s engine, and Word scales images to match the system scale factor. A 200px-wide logo gets stretched to 250px or 300px on screen. If the image file is only 200px wide, those extra pixels are invented by interpolation — that’s the blur.

2. Missing explicit dimensions. When an <img> tag has no width/height attributes, Outlook decides the display size itself — using the image file’s DPI metadata. An image saved at 72 DPI (the default in many design tools) renders roughly 133% larger than its pixel dimensions, because Outlook assumes 96 DPI. An image saved at 220 DPI renders much smaller, then may get scaled back up elsewhere. Either way, the size you designed is not the size that renders.

3. Resampling on send. Classic Outlook doesn’t just display images scaled — when you send, it can permanently re-encode embedded images to 96 DPI at their rendered size. So even recipients on perfectly normal displays receive the degraded version. This is why a signature that looked acceptable on your screen arrives blurry in someone’s inbox.

The fix: 2x export + locked dimensions

The recipe that survives all three problems:

1. Export your logo at twice the display size. If it should appear 100px wide, export a 200px-wide file. The extra pixels mean that when Windows scaling stretches the image to 125–150%, there’s real detail to draw instead of interpolated mush. This also makes it sharp on high-DPI (“Retina”) screens in every other client.
2. Set width and height attributes to the display size (100, not 200). HTML attributes are the only sizing Outlook’s Word renderer reliably respects.
3. Repeat the dimensions in inline CSS. Gmail, Apple Mail, and Outlook on the web respect CSS; classic Outlook respects attributes. You need both, and they must agree.
4. Use PNG, not JPG. Logos are hard-edged shapes and text. JPG compression creates ringing artifacts around edges that get amplified by every resample. PNG is lossless and supports transparency.

Here’s what a correctly armored logo tag looks like — a 200×80px PNG displayed at 100×40:

<img src="logo.png"
     width="100" height="40"
     alt="Acme Co"
     style="width:100px;height:40px;display:block;border:0;" />

The pixel file is 2x; the attributes and the CSS both say the display size; display:block prevents the stray gap some clients add under images. With dimensions locked on both channels, Outlook has no decision to make — it draws the image at 100×40 regardless of DPI metadata or display scaling, and the 2x source keeps it crisp when the OS scales the rendering.

Things that don’t fix it

• Re-saving the image at a higher DPI alone. DPI metadata only matters when dimensions are missing. Fix the dimensions and DPI becomes irrelevant.
• Resizing the image by dragging inside Outlook’s signature editor. This is the worst option — Outlook resamples the bitmap on the spot and bakes the blur in.
• Switching to JPG “for quality.” JPG quality settings control photo compression; for flat logo art, even maximum-quality JPG is worse than PNG.
• Using an enormous image and letting Outlook shrink it. Downscaling without locked dimensions still triggers Outlook’s lossy resample on send, and you risk blowing past size limits.

If you’re pasting a signature into Outlook, the install method matters too — the new Outlook, Outlook on the web, and classic Outlook each handle HTML differently. Our classic Outlook guide covers placing a .htm file directly into the %APPDATA%\Microsoft\Signatures folder, which bypasses the paste step entirely, and there’s a separate walkthrough for the new Outlook, which only accepts pasted rich text.

Or skip the hand-coding

This is exactly the kind of fiddly, easy-to-regress detail OnceSig handles automatically. Every image in every template is exported with explicit width/height attributes and matching inline CSS dimensions, sized for 2x source files, inside a table-based layout with mso-line-height-rule:exactly on every line — the full set of defenses Outlook’s Word renderer requires. The editor is free to use; a one-time license ($9 for one signature, no subscription, no account) removes the small credit line from exports. Your signature data never leaves your browser.

Either way — hand-coded or generated — the rule is the same: 2x pixels, display-size attributes, matching CSS, PNG. Lock all four and the blur is gone on every screen.